pubsub-execd

Cron like daemon process that triggers executables based on messages received from pubsub topic.

Configuration

Define the triggers in configuration file.

logging:
  output: stdout
triggers:
  - name: echo stuff
    run:
      timeout: 1h
      concurrency: 1
      exec: /bin/echo
      args:
        expression: {{ .Attributes.foobar }} {{ .Payload.foo.bar }}
    pubsub:
      project: sample123
      subscription: execd
  - name: date with format
    run:
      timeout: 20s
      concurrency: 1
      exec: date
      args:
        expression: +{{ .Attributes.format }}
    pubsub:
      project: sample123
      subscription: execd

logging spec:

• output - define the log output, accepted values are none, syslog, stdout and stderr. Default is stdout.

run spec:

• timeout - if the message is not ack in this time, it will be redelivered to subscription
• concurrency - for receiving and processing messages for same trigger in parallel
• exec - executable
• args.expression - go-template to parse the received message. The attributes are stored as .Attributes and if the received data is in json format, it is stored in .Payload.

pubsub spec:

• project - project id from where subscription should be found
• subscription - subscription name

n.b pubsub-execd does not create subscriptions, and they must exist before using them in configuration.

Running

pubsub-execd -f /path/to/config.yaml

Example

1. Setup topic execd-demo-topic with subscription exec-demo-sub in your project.
2. Start the daemon:

pubsub-execd -f sample.yaml

3. Send message to topic:

gcloud pubsub topics publish \
    --project=sample-project-123 execd-demo-topic \
    --message='{"foo": {"bar": "and-this" }, "foobar": "not printed"}' \
    --attribute=foobar=print-this,not=printed

4. Expected output from daemon process:

2025/01/27 09:08:26 Running command: /bin/echo print-this and-this
print-this and-this
2025/01/27 09:08:26 Command /bin/echo executed successfully